[llvm] [LiveDebugVariables] Add basic verification (PR #79846)

[Jay Foad via llvm-commits]

================
@@ -492,6 +492,13 @@ class UserValue {
   /// Return DebugLoc of this UserValue.
   const DebugLoc &getDebugLoc() { return dl; }
 
+  void verify() const {
+    for (auto I = locInts.begin(), E = locInts.end(); I != E; ++I) {
----------------
jayfoad wrote:

I don't think this works because I need to call `start` and `stop` which are methods on the iterator itself (an instance of `IntervalMap::const_iterator`).

https://github.com/llvm/llvm-project/pull/79846